CN113574022B

CN113574022B - Membrane separation process

Info

Publication number: CN113574022B
Application number: CN202080021013.0A
Authority: CN
Inventors: 小森英之; 早川邦洋; 鲁映红; 张智皓; 沈丽暖; 何嘉欣
Original assignee: Kurita Water Industries Ltd; Nanyang Technological University
Current assignee: Kurita Water Industries Ltd; Nanyang Technological University
Priority date: 2019-03-29
Filing date: 2020-03-13
Publication date: 2023-12-29
Anticipated expiration: 2040-03-13
Also published as: CN113574022A; EP3950602A4; TW202037566A; JP2020163271A; EP3950602B1; EP3950602A1; WO2020203168A1; JP7220112B2; KR20210137479A; SG11202109824TA

Abstract

The main object of the present invention is to provide a membrane separation method capable of inhibiting the activity of microorganisms in a biofilm present on a reverse osmosis membrane and stably and continuously performing water treatment for a long period of time. The present invention provides a membrane separation method for performing membrane separation treatment by intermittently adding a chlorine-binding agent containing a sulfamic acid compound to water to be treated supplied to a reverse osmosis membrane separation apparatus, wherein the intermittent addition is performed repeatedly during an intermittent addition water supply period in which the chlorine-binding agent is added to the water to be treated at a concentration that inhibits the activity of microorganisms in a biofilm and water is supplied to the reverse osmosis membrane separation apparatus, and during a no-addition water supply period in which water is supplied to the reverse osmosis membrane separation apparatus without adding the chlorine-binding agent, and the time of the intermittent addition water supply period is 0.25 to 5 hours and the time of the no-addition water supply period is 1 to 6 hours.

Description

Membrane separation process

Technical Field

The present invention relates to a membrane separation method.

Background

Membrane treatment is performed to remove impurities and ions from various industrial drainage, domestic drainage, and other drainage, surface water, and groundwater. Further, the system for performing the membrane treatment is widely used in an ultrapure water production process, a drain recycling process, and a seawater desalination process using industrial water, tap water, drain water, and the like as raw water.

However, when membrane treatment is performed by a permeable membrane such as a reverse osmosis membrane (RO membrane), the water to be treated contains contaminants such as turbidity matters, organic matters, and microorganisms. The permeable membrane is contaminated with these contaminants, and clogging of the permeable membrane occurs, which causes problems such as a decrease in the permeation flux and a decrease in the separation rate. Thus, in the membrane separation device or the membrane separation system, the water treatment cannot be stably continued for a long period of time. For this reason, for example, in order to stably perform membrane separation over a long period of time, the following membrane separation method has been proposed.

For example, patent document 1 discloses a membrane separation method in which a combined chlorine agent composed of a chlorine-based oxidizing agent and a sulfamic acid compound is present in water or a detergent supplied to a membrane separation apparatus.

As the sulfamic acid compound, R in the amide sulfuric acid represented by the following formula (1) is exemplified ¹ 、R ² Examples of the chlorine-based oxidizing agent include chlorine gas, chlorine dioxide, hypochlorous acid or salts thereof, and the like.

R ¹ R ² NSO ₃ H (1)

For example, patent document 2 discloses a method in which a sulfamic acid compound-containing chlorine-binding agent is added to a water supply of a membrane separation apparatus to perform membrane separation treatment, wherein a normal chlorine-binding agent is added at a rate of 2 to 10 times the addition rate of the chlorine-binding agent, and at this time, Z represented by the following formula (2) is 1.0 < Z < 2.0.

Z＝(Mo×T+Mx×Tx)/(Mo×T) (2)

( In the formula (2), mo: concentration of combined chlorine agent of water supply when added in normal oxidation combined chlorine agent addition amount, T: water-on time, mx: the concentration of the binding chlorine agent of the water supply when the binding chlorine agent is added in an amount of 2 to 10 times the addition amount of the normal binding chlorine agent, tx: and (3) introducing water at the combined chlorine concentration Mx of the water supply. )

For example, patent document 3 discloses a membrane separation method for performing membrane separation treatment by adding a binding chlorine agent containing a sulfamic acid compound to water to be treated supplied to a membrane separation apparatus intermittently, wherein the number of viable bacteria (log cfu/mL) of the water to be treated is 3 or more, the intermittent addition is a period of water supply in which no addition of the binding chlorine agent is repeated, and a period of water supply in which intermittent addition of the binding chlorine agent is performed at a concentration at which biofilm is peeled off by initial addition of the biofilm forming agent during the period of water supply without addition, the period of water supply without addition is 6 to 120 hours, the period of water supply with intermittent addition is 0.5 to 40 hours, and the concentration of the binding chlorine agent of the water to be treated during the period of water supply with intermittent addition is a concentration of total chlorine of 0.5 to 20 mg/L.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2006-263510.

Patent document 2: japanese patent application laid-open No. 2010-201312.

Patent document 3: international publication 2013/005787.

Disclosure of Invention

Problems to be solved by the invention

The main object of the present invention is to provide a reverse osmosis membrane separation method capable of inhibiting the activity of microorganisms in a biofilm and stably and continuously performing water treatment for a long period of time.

Means for solving the problems

In a permeable membrane such as an RO membrane, since water as a solvent permeates the membrane, a solute is concentrated on a membrane surface, microorganisms adhere to the membrane surface, and microorganisms remaining on the membrane surface secrete polysaccharides, proteins, and the like to form a biological membrane. When the microorganisms in the biofilm are placed to continue membrane separation, the biofilm grows thicker by the action of the microorganisms in the biofilm. The biofilm grows on the membrane surface, so that the membrane is blocked, the differential pressure rises, the flux is reduced, and finally, the membrane separation cannot be stably performed for a long time, and the water treatment cannot be continuously performed. Therefore, in the case of a decrease in flux or in the case of periodic washing or replacement of the permeable membrane, from the viewpoints of costs and workability due to washing or replacement of the permeable membrane, it is desired that the operation can be continued for a long period of time without washing or replacement of the permeable membrane as much as possible.

As described above, microorganisms are present in the biofilm attached to the reverse osmosis membrane for membrane separation, and the microbial activities therein may cause the formation of the biofilm. Accordingly, the present inventors focused on the inhibition of the activity of microorganisms in a biofilm as a new method, and studied whether or not the water treatment can be continued stably by a reverse osmosis membrane for a long period of time.

Accordingly, the present inventors produced a model of a case where microorganisms were attached to a reverse osmosis membrane and the microorganisms were moving in a biofilm by incubating the reverse osmosis membrane and the microorganisms together.

Then, the present inventors have conducted intensive studies using this incubation model, and as a result, have found that the use of a sulfamic acid compound-containing chlorine binding agent (hereinafter also referred to as "chlorine binding agent") for a reverse osmosis membrane containing a biofilm under short-term intermittent addition conditions can inhibit the activity of microorganisms in the biofilm (in particular, the activity of biofilm formation by microorganisms). As short-term intermittent addition conditions in this case, the time of the intermittent addition water supply period and the time of the no-addition water supply period (specifically, these periods are repeated for 1 round) are shortened, respectively. Thus, the present inventors completed the present invention.

That is, the present invention is described in the following (1) to (9).

(1) A membrane separation method for performing membrane separation treatment by intermittently adding a chlorine-binding agent containing a sulfamic acid compound to water to be treated supplied to a reverse osmosis membrane separation device, wherein the intermittent addition is performed repeatedly during an intermittent addition water supply period in which the chlorine-binding agent is added to the water to be treated at a concentration that inhibits the activity of microorganisms in a biofilm and water is supplied to the reverse osmosis membrane separation device, and during a non-addition water supply period in which water is supplied to the reverse osmosis membrane separation device without adding the chlorine-binding agent, the intermittent addition water supply period is 0.25 to 5 hours, and the non-addition water supply period is 1 to 6 hours.

(2) The membrane separation method according to the above (1), wherein when one intermittent water supply period and one non-additive water supply period are taken as one cycle, the time of the one cycle is 1.25 to 11 hours.

(3) The membrane separation method according to the above (1) or (2), wherein the time ratio of the non-addition water supply period to the intermittent addition water supply period is 0.2 to 24.

(4) The membrane separation method according to any one of (1) to (3), wherein the intermittent addition water supply period is 0.5 to 1 hour and/or the no addition water supply period is 1 to 4 hours.

(5) The membrane separation method according to any one of (1) to (4), wherein when one intermittent water supply period and one non-addition water supply period are taken as one cycle, an average concentration of the chlorine-binding agent in the water to be treated is 0.05 to 1.5mg/L in terms of the chlorine-binding amount per one cycle.

(6) The membrane separation method according to any one of (1) to (5), wherein the membrane separation method is operated in a range of 0 to 50000mg/L of salt concentration in the water to be treated.

(7) The membrane separation method according to any one of (1) to (6), wherein chlorine-based oxygen in the water to be treated during the intermittent addition of water supplyThe composition ratio of the catalyst to the alkali metal component was 2X 10 in terms of Cl/alkali metal molar ratio ^-5 ～1×10 ^-3 。

(8) The membrane separation method according to any one of (1) to (7), wherein the ratio of Br to Cl in the water to be treated during the intermittent addition of water supply is 5X 10 in terms of molar ratio of Br/Cl ^-3 The following is given.

(9) The membrane separation method according to any one of (1) to (8), wherein the membrane surface of the separation membrane is operated so that the flow rate becomes 4 cm/sec to 15 cm/sec.

Further, patent document 1 discloses that the above-mentioned chlorine-binding agent is added at all times or intermittently, but in practice, in examples, it is disclosed that the object can be achieved by adding the above-mentioned chlorine-binding agent at all times. In addition, paragraph [0006] of patent document 1 describes that the bactericidal activity of chloramine is weaker than that of free chlorine by about 1/50 to 1/200. As described above, patent document 1 generally describes that a chlorine-binding agent composed of a chlorine-based oxidizing agent and an sulfamic acid compound needs to be added at all times to prevent contamination of a permeation membrane due to proliferation of microorganisms. Therefore, according to patent document 1, short-term intermittent addition conditions in the present invention are not realized, specifically, a period during which no water is supplied and a period during which water is supplied are intermittently added are not realized to be short periods.

In addition, patent document 2 discloses that in the example, in the process of continuously adding the sulfamic acid compound-containing chlorine-binding agent, a high concentration of usually 2 to 10 times the amount is added at a time of 30 days over a 24-hour period. As described above, it is generally understood that in patent document 2, the binding chlorine agent containing the sulfamic acid compound is added at a normal concentration and then added at a high concentration, and therefore, it is necessary to always add the binding chlorine agent. Therefore, according to patent document 2, the short-term intermittent addition condition in the present invention is not achieved, specifically, the non-addition water supply period and the intermittent addition water supply period are not achieved to be short-term.

Further, patent document 3 discloses a method of performing membrane separation processing by repeating a non-addition water supply period and an intermittent addition water supply period, wherein water is supplied without adding a binding chlorine agent during the non-addition water supply period, and wherein a binding chlorine agent of a concentration that causes biofilm to peel off is added and supplied at an initial stage of biofilm formation during the intermittent addition water supply period. As described above, in patent document 3, intermittent addition conditions are set by intensively studying the peeling of the biofilm and the initial stage of formation of the biofilm, but at this initial stage, it is difficult to describe the state of positive activity of microorganisms. That is, in patent document 3, from the viewpoint of inhibiting the activity of microorganisms in a biofilm (in particular, the activity of biofilm formation by microorganisms), it cannot be said that the condition setting is sufficient. Therefore, the short-term intermittent addition condition in the present invention is newly found from a method completely different from that of patent document 3, and according to patent document 3, the short-term intermittent addition condition in the present invention is not achieved, specifically, the non-addition water supply period and the intermittent addition water supply period are not achieved, respectively, in a short period.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a reverse osmosis membrane separation method capable of inhibiting the activity of microorganisms in a biofilm and stably and continuously performing water treatment for a long period of time can be provided.

The present invention is not limited to the effects described herein, and may be any effects described in the present specification.

Drawings

Fig. 1 is a flow chart of an aqueous system in which a chlorine binding agent is added simultaneously or separately to a preceding stage of a reverse osmosis membrane treatment system as an example of an embodiment of the present invention.

FIG. 2 shows the change in microbial activity (FIG. 2A: protein amount; FIG. 2B: viable count; FIG. 2C: total ATP amount) during the intermittent addition of water supply for 0.5 hours and during the no-addition of water supply for 0 to 6.5 hours. The horizontal axis represents the total time (h) between the intermittent water supply period and the no-water supply period, which is the total time from the time when the chemical is added.

Fig. 3 is a schematic diagram showing the configuration of the apparatus in the water system test.

Fig. 4 shows changes in membrane pressure when intermittent addition conditions are changed in a water system using a reverse osmosis membrane. The first half was run during intermittent feed of water (1 h; combined chlorine addition to combined chlorine meter 1.2-2.4 mg/L) and during no feed of water (7 h). The latter half was operated during the intermittent addition of water supply of the present invention (0.5 h; combined chlorine addition to combined chlorine meter 2.4-1.8 mg/L) and during no addition of water supply (3.5 h).

Detailed Description

The following describes modes for carrying out the present invention. It should be noted that the following described embodiment illustrates one example of a representative embodiment of the present invention and should not be construed as limiting the scope of the present invention. The upper limit and the lower limit of the numerical values may be arbitrarily combined as necessary.

1. The membrane separation method of the invention

The membrane separation method of the present invention provides a method of performing membrane separation treatment by adding a chlorine-binding agent containing a sulfamic acid compound (hereinafter also referred to as "the chlorine-binding agent") to water to be treated, which is supplied to a reverse osmosis membrane separation apparatus (or reverse osmosis membrane separation step).

Further, it is preferable that the intermittent addition is repeated between an intermittent addition water supply period in which the chlorine-binding agent is added to the water to be treated at a concentration that inhibits the microbial activity in the biofilm and water is supplied to the reverse osmosis membrane separation device and a non-addition water supply period in which water is supplied to the reverse osmosis membrane separation device without adding the chlorine-binding agent. The membrane separation process is preferably performed by alternately repeating these intermittent water supply period and non-addition water supply period.

Further, it is preferable that the intermittent water supply period is 0.25 to 5 hours, and the non-addition water supply period is 1 to 6 hours.

In this case, it is preferable that a chlorine-binding agent containing a sulfamic acid compound is added to the water to be treated during the intermittent water supply period so that the concentration of the chlorine-binding agent is 0.3 to 10mg/L.

Thus, in the reverse osmosis membrane separation method of the present invention, the activity of microorganisms in the biofilm can be suppressed and the water treatment can be stably continued for a long period of time. The present invention is not limited to the effects described herein, and may be any effects described in the present specification.

In the present invention, the combination of the chlorine-binding agent and the short-term intermittent addition condition has an advantage that the activity of microorganisms present in the biofilm can be suppressed even if the microorganisms are present in the biofilm, as will be described in the following examples. In general, the presence of microorganisms in a biofilm may cause insufficient performance of the effects of a bactericide, an antiseptic (bacteriostatic agent) and the like, and by combining the chlorine-binding agent of the present invention with short-term intermittent addition conditions, the activity of forming a biofilm can be inhibited in an appropriate amount without adding a large amount of a chemical, and the amount of biofilm formation by microorganisms causing membrane clogging can be reduced.

< 1-1. Isolation method of the invention >

The present invention relates to a method for performing membrane separation by supplying water to be treated to a system having membrane separation (hereinafter, also referred to as "membrane separation system") or a membrane separation apparatus. In the present invention, membrane separation is performed by intermittently adding a chlorine-binding agent containing a sulfamic acid compound for a short period of time in order to inhibit the activity of microorganisms in a biofilm. Thus, even if a biofilm is present on the transmission film, the activity of microorganisms in the biofilm can be suppressed, and in particular, the activity of biofilm formation by microorganisms can be suppressed. Further, in the present invention, it is more preferable that the membrane separation process is designed such that the chlorine-binding agent reaches a predetermined concentration (in terms of chlorine-binding agent) in the water supply for membrane separation, and thus the membrane separation process can be performed stably for a long period of time.

More specifically, the present invention provides a method for performing membrane separation by supplying water to be treated to a membrane separation system or a membrane separation apparatus having a permeable membrane such as a reverse osmosis membrane (hereinafter also referred to as "RO membrane"). The invention is particularly suited for membrane separation processes utilizing RO membranes. In the present specification, the term "membrane separation system or membrane separation apparatus" is also referred to as "membrane separation process".

Preferably, the present invention adds a chlorine-binding agent containing a sulfamic acid compound to water to be treated under short-term intermittent addition conditions to supply water to the RO membrane separation apparatus or RO membrane separation system. In the present invention, it is preferable to add a chlorine-binding agent containing a sulfamic acid compound (hereinafter, also referred to as "the chlorine-binding agent") to the water to be treated in order to inhibit the activity of microorganisms in the biofilm.

In the present invention, by adding the chlorine-binding agent to water to be treated under intermittent addition conditions for a short period of time, even if a biofilm is present on the RO membrane, the microorganisms present in the biofilm are further affected, and thus the activity of the microorganisms, in particular, the activity of biofilm formation by the microorganisms can be further inhibited. In the present invention, the thickness of the biofilm that is present by adhering to the RO membrane can be suppressed.

In the present invention, it is preferable that the intermittent addition is performed for a short period of time in an early stage when the biofilm is not sufficiently formed on the RO membrane, whereby the amount of biofilm caused by the membrane clogging can be further reduced.

In general, a biofilm, which is a problem in membrane separation by membrane treatment, has adhesiveness and adheres to a substrate such as a permeation membrane. The highly adhesive biofilm also adsorbs other particles (specifically, turbidity components such as organic and inorganic substances) contained in the water to be treated, and further, causes membrane clogging easily.

However, in the present invention, since the activity of microorganisms in the biofilm (in particular, the activity of biofilm formation by microorganisms) can be suppressed, the amount of biofilm formation is suppressed, and the amount of biofilm in the water to be treated or on the reverse osmosis membrane can be reduced.

According to this, the amount of the biofilm in contact with the permeable membrane can be suppressed, so that the membrane clogging due to the biofilm can be further prevented, and the membrane separation can be performed stably for a long period of time. The present invention can provide a membrane separation method capable of stably and continuously performing water treatment for a long period of time.

< 1-2. Activity of microorganisms in the present invention >

In the present invention, as an index for confirming the activity of inhibiting microorganisms, the number of viable bacteria, the total ATP amount, and the protein amount are used as indexes, and the index is not limited thereto.

Microorganisms attached to a substrate (e.g., RO membrane) are activated to form a biofilm in the cell, and the number of microorganisms and the amount of biofilm are further increased, so that the microorganisms attach to the substrate, thereby securing a living circle.

The biofilm contains extracellular polysaccharide bodies, which are also called glycoproteins, peptidoglycans, and the like, and the biofilm contains proteins and peptides.

In addition, if the microorganism produces proliferation activity such that the number of living bacteria increases, the total amount of the biofilm also tends to increase.

In addition, when microorganisms undergo such activities as proliferation and biofilm formation, the total ATP amount in the microorganisms is also liable to increase.

In view of such a situation, in the present invention, the present inventors have considered that by measuring at least one of the amount of protein, the number of viable bacteria, and the total ATP amount, inhibition of the activity of microorganisms (in particular, inhibition of the activity of biofilm formation by microorganisms) can be studied with high accuracy.

< 1-3. Reverse osmosis membrane of the invention >)

The reverse osmosis membrane (including Nanofiltration (NF) membrane) according to the present invention is particularly effective for polyamide, particularly, polymer membranes having nitrogen-containing groups such as aromatic polyamide, polyurea, and polypiperazine amide having low chlorine resistance, and may be cellulose acetate-based or other RO membranes. Examples of the permeable membrane include cellulose-based materials such as cellulose acetate, cellulose triacetate, cellulose nitrate, and cellulose; nitrogen-containing groups such as Polyacrylonitrile (PAN), aromatic polyamide (aromatic and aliphatic), and Polyimide (Polyimide); polycarbonates, polyethylene terephthalates, polyvinyl alcohols, and the like.

The reverse osmosis membrane of the present invention is not particularly limited, and may be in the form of a spiral, hollow fiber, flat membrane, or the like, and the skin layer may be made of a resin such as cellulose acetate, aromatic polyamide, polyimide, or the like.

The membrane separation device or the membrane separation system of the present invention can be added to a water treatment system using natural water such as seawater, river water, well water, lake water, or the like, industrial water, tap water, drain water, or the like as raw water, and can be added to a water treatment system such as a seawater desalination process, an ultrapure water treatment manufacturing process, a drain water reuse process, or the like.

< 1-4. Treated Water >

In the present invention, as the water to be treated which is supplied to the membrane separation apparatus or the membrane separation system to be subjected to membrane separation, for example, sea water, river water, well water, lake water, industrial water, city water, drain water and the like are given as the object of all water which can be subjected to membrane separation by passing through the membrane. The water to be treated may contain microorganisms such as bacteria.

The pH of the water to be treated is not particularly limited, but is preferably 3 to 9, and can be appropriately adjusted by an acid or a base. The water temperature of the water to be treated is usually about 4 to 40 ℃, and the present invention is not limited thereto.

1-4a. Number of viable bacteria in treated Water >)

In the present invention, by suppressing the activity of microorganisms present on the permeable membrane, the amount of biofilm formed can be reduced, and the total amount of biofilm in contact with the permeable membrane can be reduced. In the present invention, it is preferable to perform intermittent addition for a short period of time in an early stage when the biofilm is not sufficiently formed, because the total amount of the biofilm can be reduced.

In the present invention, the amount of the biofilm formed is small, and from the viewpoint of stably and continuously performing membrane separation for a long period of time, the chlorine binding agent is preferably added. In addition, from the viewpoint of high efficiency of using the chemical, it is preferable to start adding the chlorine binding agent before forming a large amount of biofilm.

The number of living bacteria can be appropriately controlled by a method of inhibiting the number of microorganisms, and various agents such as a bactericide or an antiseptic can be used, and a sterilizing device (for example, a UV sterilizing device) can be used without particular limitation.

The chlorine-binding agent can be used for water to be treated under severe conditions in which the number of bacteria is large and the adhesion potential of the biofilm is high. Therefore, in the present invention, the number of viable bacteria (log count/mL) in the water to be treated is preferably 4 or more, more preferably 5 or more, and the upper limit value of the number of viable bacteria can be set to about 6.

Method of determination of log count/mL

In the present invention, the bacterial count (log count/mL) of the water to be treated can be measured by flow cytometry analysis described below as < method of counting the number of living bacteria >. Here, log means log of common logarithm ₁₀ 。

1-4b salt concentration in treated Water

The concentration of salt in the water to be treated is not particularly limited, and for example, in the present invention, in addition to low-salt water to be treated such as fresh water and tap water, even water to be treated having a high concentration of salt (for example, soda water, seawater, water mixed with salt, or the like) can be stably subjected to membrane separation for a long period of time. In the present invention, the salt concentration in the water to be treated can be adjusted to a predetermined range, and for example, the water can be operated in a preferable range of 0 to 50000mg/L, and in general, the salt concentration is in a range of approximately 25000 to 50000mg/L when sea water is used as the water to be treated, and the salt concentration is in a range of approximately less than 25000mg/L when tap water, fresh water, or the like is used as the water to be treated.

Method for measuring salt concentration

The salt concentration can be measured by a salt meter that measures the conductivity.

According to the present invention, even when various raw water is used as water to be treated, the membrane separation can be stably performed over a long period of time while suppressing the activity of microorganisms in the biofilm existing on the reverse osmosis membrane.

< 1-5. Chlorine-binding Agents used in the present invention >

In the present invention, the chlorine-binding agent added to the water to be treated is a chlorine-binding agent containing a sulfamic acid compound. Examples of the chlorine-binding agent used in the present invention include those described in WO2011/125762 (reference 1) and WO2013/005787 (patent document 3).

Method for measuring free chlorine concentration, bound chlorine concentration and perchloric concentration

In the present invention, the free chlorine concentration, the combined chlorine concentration and the perchloric concentration pass through JIS K0400-33-10:1999 DPD method using N, N-diethyl-1, 4-phenylenediamine in Cl ₂ Concentration was measured in terms of concentration. In JIS K0400-33-10:1999, the following definitions are given.

That is, the free chlorine is chlorine in the form of hypochlorous acid, hypochlorite ion, or dissolved chlorine. The bound chlorine is chlorine in the form of chloramine, organic chloramine, or the like, which is not contained in the above-mentioned free chlorine but is perchloric as measured by the DPD method. Perchloric is chlorine in the form of free chlorine, bound chlorine, or both.

1-5a. Incorporate chlorine agent >

The chlorine-binding agent used in the present invention is preferably a reagent measured as the above-described chlorine-binding agent, and more preferably a chlorine-binding agent comprising an aqueous solution preparation containing a base composed of an alkali metal hydroxide, a sulfamic acid compound, and a chlorine-based oxidizing agent. The aqueous formulation may be used directly as a chlorine-binding agent.

The composition ratio of the chlorine-based oxidizing agent to the sulfamic acid compound in the aqueous solution preparation is preferably 0.3 to 0.7, more preferably 0.4 to 0.6 in terms of the molar ratio of Cl/N.

The composition ratio of the chlorine-based oxidizing agent to the alkali metal component in the aqueous solution preparation is preferably 0.15 to 0.5, more preferably 0.2 to 0.4 in terms of the molar ratio of Cl/alkali metal.

The concentration of free chlorine in the aqueous solution preparation is preferably 2 mass% or less of the total chlorine concentration.

The aqueous solution preparation preferably has a pH of 13 or more, and the composition ratio of the sulfamic acid compound to the base in the aqueous solution preparation is preferably 0.4 to 0.7 in terms of a molar ratio of N/alkali metal.

Preferably, the above-mentioned Cl/N molar ratio corresponds to that obtained by the above-mentioned JIS K0400-33-10: cl of chlorine-based oxidizing agent measured in 1999 ₂ The ratio of the number of moles of the sulfamic acid compound composed of N. In addition, the molar ratio of N/alkali metal is preferably equivalent to the molar ratio of the sulfamic acid compoundThe ratio of the number to the number of moles of the base consisting of the alkali metal hydroxide.

The upper limit and the lower limit of each constituent component of the aqueous solution preparation may be arbitrarily combined as desired.

1-5b sulfamic acid combined with chlorine agent

The sulfamic acid constituting the sulfamic acid compound of the chlorine-binding agent is preferably selected from the group consisting of R ¹ R ² NSO ₃ Amide sulfuric acid represented by H (1). R in the formula (1) ¹ 、R ² Each independently is preferably H or a hydrocarbon group having 1 to 6 carbon atoms. As such sulfamic acid, R is more preferable ¹ 、R ² "sulfamic acid" in the narrow sense of H, N-methyl sulfamic acid, N-dimethyl sulfamic acid, N-phenyl sulfamic acid, and the like can also be used. The sulfamic acid compound may be used in the form of a free (powdery) acid, or may be a salt such as an alkali metal salt, e.g., sodium salt or potassium salt.

1-5c alkali component in combination with chlorine agent

The alkali component constituting the chlorine binding agent is preferably an alkali composed of an alkali metal hydroxide, but is not limited thereto. Examples of the alkali metal hydroxide include sodium hydroxide salt and potassium hydroxide salt.

Examples of the chlorine-based oxidizing agent include hypochlorous acid, chlorous acid, or a soluble salt such as an alkali metal salt thereof, and more preferably, a chlorine-based oxidizing agent containing no sodium chloride in any of these agents. Preferably, the sodium chloride in the aqueous solution preparation is controlled to 50000mg/L or less, whereby precipitation of salts can be prevented and the stability of the chlorine-based oxidizing agent can be improved.

The above-mentioned chlorine binding agent can be prepared by adding a sulfamic acid compound to an aqueous alkali solution composed of an alkali metal hydroxide to dissolve the sulfamic acid compound, and adding a chlorine-based oxidizing agent to the resulting aqueous sulfamic acid compound-alkali mixed solution to mix the mixture, thereby preparing an aqueous solution preparation. The prepared aqueous solution preparation may also be used as a chlorine-binding agent.

For the aqueous alkali solution, the amount of water is preferably 50 to 65% by mass.

The alkali is composed of an alkali metal hydroxide, and examples of such alkali include sodium hydroxide, potassium hydroxide, and the like, which maintain solubility when the aqueous solution of the chlorine-binding agent is prepared.

< 1-5d. Morphology of sulfamic acid Compound bound to chlorine Agents >)

The sulfamic acid compound may be added as a salt, and examples of the salt that can be used in this case include salts that are soluble when the above-described aqueous solution of the coupling chlorine agent is prepared. As the salt, for example, 1 or 2 or more kinds of salts selected from sodium sulfamate, potassium sulfamate, ammonium sulfamate, and the like can be used.

The sulfamic acid compound is preferably added so that the sulfamic acid compound concentration in the aqueous solution formulation reaches the above concentration.

The amount of the sulfamic acid compound to be added is preferably 0.4 to 0.7 in terms of the molar ratio of the base to the alkali metal.

The sulfamic acid compound may be added with sulfamic acid or a salt thereof in the form of powder or in the form of an aqueous solution. In the case of using sulfamate, the amount of alkali metal contained in sulfamate is added as the alkali of Cl/alkali metal, N/alkali metal. In the case of using an aqueous solution, the amount of water contained in the aqueous solution is added as the amount of water of the aqueous alkali solution.

The chlorine-based oxidizing agent is preferably hypochlorous acid or a salt thereof, and is effective chlorine (Cl) ₂ ) The concentration is preferably 1% by mass or more, more preferably 5% by mass or more, and the upper limit is preferably 25% by mass or less, more preferably 20% by mass or less, and is preferably 5 to 20% by mass, more preferably 10 to 15% by mass of the aqueous solution. The upper limit value and the lower limit value of each constituent component may be arbitrarily combined as desired.

The amount of the chlorine-based oxidizing agent to be added is such that the concentration of the chlorine-based oxidizing agent in the aqueous solution preparation is set as available chlorine (Cl) ₂ ) The concentration reaches the above concentration and the composition ratio of the chlorine-based oxidant and the sulfamic acid compound is calculated as the mole ratio of Cl/NThe ratio is added. Thus, the chlorine-bonded agent comprising an aqueous solution preparation excellent in reactivity, stability, handleability, and free of chlorine smell can be efficiently produced without generating foaming or chlorine smell. In this case, it is also preferable to add the chlorine-based oxidizing agent slowly and mix them. When the chlorine-based oxidizing agent is an alkali metal salt, the amount of the alkali metal is added as the alkali of the Cl/alkali metal or N/alkali metal.

The above-mentioned chlorine-binding agent is added to water to be treated for chlorine treatment, and the concentration of free chlorine in the preparation is low and the concentration of bound chlorine is high as described above, and therefore, the concentration of bound chlorine can be increased by adding such a preparation to an aqueous system to decrease the concentration of free chlorine. The permeation of the combined chlorine into the biofilm is higher than that of the free chlorine, and the adhesiveness of the adhesive substance can be reduced from the inside. The chlorine-binding agent of the present invention can inhibit the activity of microorganisms.

The chlorine treatment can be performed by adding the chlorine-binding agent to the water to be treated supplied to the membrane separation device or the membrane separation system so that the upper limit of the concentration of the chlorine-binding agent in the water to be treated is preferably 10mg/L or less, more preferably 5mg/L or less, still more preferably 3mg/L or less, and further preferably 0.3mg/L or more.

In this case, the concentration of free chlorine in the water to be treated is preferably 0.3mg/L or less, more preferably 0.1mg/L or less, and still more preferably 0.05mg/L or less. As described above, by setting the free chlorine concentration to be low, deterioration of the RO membrane can be prevented.

In the present invention, since the free chlorine concentration in the water to be treated is low as described above, the total chlorine concentration in the water to be treated is substantially equal to the combined chlorine concentration.

When the above-mentioned chlorine-binding agent is used as a membrane-permeable mucilage control agent such as an RO membrane, it is added to water to be treated to reduce the concentration of free chlorine and to increase the concentration of bound chlorine, and therefore, it is possible to increase the concentration of available chlorine and to suppress the activity of forming a biofilm even in water under severe conditions where the number of viable bacteria is large and the potential of microbial activity is high, and thus, clogging of the membrane can be prevented. By using the above-mentioned chlorine-binding agent, the activity of forming a biofilm of the water to be treated having a large number of living bacteria can be prevented from being increased by adding the agent as the chlorine-binding agent at a high concentration.

< 1-6. Short-term intermittent addition Condition >

In the present invention, a membrane separation treatment is performed by adding a chlorine-binding agent containing a sulfamic acid compound to water to be treated under short-term intermittent addition conditions. Preferably, the short-term intermittent addition condition is performed in a short-term intermittent addition water supply period and no addition water supply period, respectively. Further, it is preferable that these intermittent water supply period and non-addition water supply period are alternately repeated. The water to be treated is supplied to a reverse osmosis membrane separation device or a reverse osmosis membrane separation system.

In the membrane separation treatment of the present invention, it is preferable that at least one cycle is contained as one cycle during one intermittent addition of water supply and one no addition of water supply. In the membrane separation process of the present invention, the one cycle may be performed continuously or intermittently plural times, and the membrane separation process may be performed under a set of operating conditions of the plural cycles. In the present invention, the membrane separation process may be performed with the short-term intermittent addition conditions of the present invention being appropriately changed with the lapse of time. In the present invention, the operation may be performed by appropriately changing the set of conditions, or a plurality of the set of conditions may be performed by appropriately combining them. In the present invention, the operation of the membrane separation process can be performed according to the change with time of the RO membrane by changing the circulation conditions and the group conditions.

The intermittent addition water supply period is a water supply period in which the chlorine-binding agent containing the sulfamic acid compound is added to the water to be treated and water is supplied to the reverse osmosis membrane separation device.

The non-addition water supply period is a water supply period during which water is supplied to the reverse osmosis membrane separation device without adding a chlorine-binding agent containing a sulfamic acid compound.

The binding chlorine agent containing the sulfamic acid compound preferably uses a concentration of binding chlorine that inhibits microbial activity in the biofilm.

As described above, by using the chlorine-binding agent for intermittent addition for a short period of time, the activity of microorganisms in the biofilm (particularly, the activity of biofilm formation by microorganisms) can be more favorably inhibited.

By setting the intermittent addition conditions for a short period in the present invention, the addition amount of the chemical is also effective in a small amount, and the biofilm-forming activity on microorganisms can be further suppressed. By repeating the non-addition water supply period and the intermittent addition water supply period, the biofilm formation activity by microorganisms can be further suppressed, and thus the total amount of biofilm is also reduced, and as a result, the adhesion amount of biofilm to the film can be reduced. In addition, the method of continuously adding a chemical at all times without using the intermittent addition condition of the short period as in the present invention is not preferable from the viewpoint of cost because the amount of the chemical increases.

Further, it is preferable that the short-term intermittent addition condition in the present invention is preferably started at or before the initial stage of biofilm formation, more preferably at or before the logarithmic proliferation period of microorganisms in the biofilm, and still more preferably at or before the stage of the acceleration period of proliferation.

In the present invention, it is preferable that the short-term intermittent addition condition starts the intermittent addition water supply period first, and the concentration of the chlorine-binding agent in the water to be treated is increased, compared with the non-addition water supply period, so that the activity of microorganisms in the biofilm is easily suppressed.

Thus, the activity of microorganisms can be effectively inhibited by a small amount of the agent, and membrane clogging due to an increase in the formation of a biofilm can be prevented.

1-6a. Intermittent addition of Water supply period >)

In the present invention, the upper limit of the length of each addition period of the intermittent addition water supply period in which the chlorine-binding agent is added to supply water is preferably 5 hours or less, more preferably 4 hours or less, still more preferably 3 hours or less, still more preferably 2 hours or less, still more preferably 1 hour or less, still more preferably 0.75 hours or less, and the lower limit thereof is preferably 0.25 hours or more, more preferably 0.3 hours or more, still more preferably 0.4 hours or more, and still more preferably 0.5 hours or more. The range of the value is preferably 0.25 to 5 hours, more preferably 0.4 to 3 hours, and even more preferably 0.5 to 1 hour. The upper limit value and the lower limit value of each constituent component may be arbitrarily combined as desired.

1-6b Each concentration in treated Water during intermittent addition of Water supply >)

During the intermittent addition of the water supply, the chlorine-binding agent is added to the water to be treated, and each constituent component in the water to be treated during the intermittent addition of the water supply can be appropriately adjusted by the water to be treated and the chlorine-binding agent added thereto. The upper limit value and the lower limit value of each constituent component in the water to be treated in the intermittent water supply period can be arbitrarily combined as desired from the ranges described in the present specification.

The combined chlorine concentration of the water to be treated in the intermittent water supply period is not particularly limited, but the lower limit is preferably 0.3mg/L or more, more preferably 0.5mg/L or more, further preferably 1.0mg/L or more, and the upper limit is preferably 10mg/L or less, more preferably 5mg/L or less, further preferably 3mg/L or less. The amount of the drug to be added is preferably 0.3 to 10mg/L, more preferably 0.5 to 5mg/L, and even more preferably 1 to 3 mg/L.

By setting the concentration to such a level, the microbial activity in the biofilm (in particular, the activity of forming the biofilm by the microorganism) can be effectively inhibited. The upper limit value and the lower limit value of each constituent component may be arbitrarily combined as desired.

The composition ratio of the chlorine-based oxidizing agent to the alkali metal component in the water to be treated during the intermittent addition of the water supply is not particularly limited, and is preferably 4X 10 in terms of the molar ratio of Cl/alkali metal ^-6 ～1×10 ^-3 More preferably 2X 10 ^-5 ～5×10 ^-4 More preferably 3X 10 ^-5 ～2.4×10 ^-4 The agent is added within the range of (2).

Preferably adding a pharmaceutical agent to cause saidThe ratio of Br to Cl in the water to be treated during the intermittent addition of the water supply is preferably 5X 10 in terms of molar ratio of Br/Cl ^-3 The following ranges.

< 1-6c during no added water supply >

In the present invention, the upper limit of the non-addition water supply period for supplying water without adding the chlorine-binding agent is 6 hours or less, more preferably less than 6 hours, still more preferably 5.5 hours or less, still more preferably 5 hours or less, still more preferably 4 hours or less, still more preferably 3 hours or less, still more preferably 2.5 hours or less, and the lower limit thereof is preferably 0.25 hours or more, still more preferably 0.5 hours or more, still more preferably 1 hour or more, still more preferably 2 hours or more. The range of the value is preferably 1 to 6 hours, more preferably 1 to 4 hours, and even more preferably 1 to 3 hours. The upper limit value and the lower limit value of each constituent component may be arbitrarily combined as desired.

1-6d average concentration of the chlorine-binding agent in the treated water

The average concentration (in terms of mg/L of bound chlorine) of the bound chlorine agent in the water to be treated in one cycle is not particularly limited, but the lower limit of the average concentration per cycle is preferably 0.05mg/L or more, more preferably 0.1mg/L or more, still more preferably 0.2mg/L or more, and the upper limit thereof is preferably 1.5mg/L or less, more preferably 1.0mg/L or less, still more preferably 0.5mg/L or less. The average concentration in each cycle is preferably in the range of 0.05 to 1.5mg/L in terms of combined chlorine, more preferably 0.1 to 1.0mg/L in terms of combined chlorine, still more preferably 0.2 to 0.5mg/L in terms of combined chlorine. The upper limit value and the lower limit value of each constituent component may be arbitrarily combined as desired.

In the present invention, one intermittent water supply period and one non-additive water supply period are referred to as one cycle, and preferably the one cycle is repeatedly performed as one unit.

The average concentration of the chlorine-binding agent in the water to be treated can be adjusted for each cycle by intermittently adding the water supply period, and by adding the chlorine-binding agent in the water supply period and the water supply period without adding the chlorine-binding agent. In addition, the circulation condition can be changed appropriately.

In the present invention, short-term intermittent addition conditions were found from the viewpoint of inhibiting the activity of microorganisms adhering to the RO membrane. Further, in the present invention, the average concentration of the chlorine-binding agent in the water to be treated in each cycle is found based on the short-term intermittent addition condition. Thus, the present invention is advantageous in terms of cost because the amount of the chlorine-binding agent to be added to the water to be treated during long-term operation can be set to a more appropriate amount than conventional continuous addition or conventional intermittent addition.

1-6e ratio of intermittent to non-additive water supply period and cycle

In the present invention, the time ratio between the no-addition water supply period and the intermittent-addition water supply period is not particularly limited, but the lower limit value thereof is preferably 0.2 or more, more preferably 0.5 or more, more preferably 2 or more, more preferably 3 or more, more preferably 4 or more, more preferably 5 or more, and the upper limit value thereof is preferably 24 or less, more preferably 20 or less, more preferably 15 or less, more preferably 10 or less. The ratio of the period of no-addition water supply to the period of intermittent addition water supply is preferably 0.2 to 24, more preferably 3 to 10, still more preferably 5 to 10, still more preferably 6 to 8. The upper limit value and the lower limit value of each constituent component may be arbitrarily combined as desired.

In the present invention, the time of one cycle is not particularly limited, but the lower limit is preferably 0.75 hours or more, more preferably 1 hour or more, still more preferably 1.25 hours or more, still more preferably 1.5 hours or more, still more preferably 2 hours or more, and the upper limit is preferably 11 hours or less, more preferably 10 hours or less, still more preferably 9 hours or less, still more preferably 8 hours or less, still more preferably 7 hours or less, still more preferably 5 hours or less, still more preferably 4 hours or less, still more preferably 3.5 hours or less.

The numerical range of the one cycle time is preferably 1.25 to 11 hours, more preferably 1.5 to 11 hours, still more preferably 1.5 to 9 hours, and still more preferably 1.5 to 5 hours.

The upper limit value and the lower limit value of each constituent component may be arbitrarily combined as desired.

< 1-6f flow Rate of Membrane surface >

In the present invention, the flow rate of the membrane surface of the separation membrane for supplying water to the membrane separation treatment is not particularly limited, and the membrane surface is preferably operated to 2 to 20 cm/sec, more preferably 4 to 15 cm/sec, and still more preferably 6 to 10 cm/sec.

2. The water treatment method of the invention

As described above, the embodiment of the present invention is a method of performing membrane separation treatment by intermittently adding a chlorine-binding agent containing a sulfamic acid compound to water to be treated, which is supplied to a reverse osmosis membrane separation apparatus or a reverse osmosis membrane separation system, for a short period of time to inhibit the activity of microorganisms in a biofilm (particularly, the activity of biofilm formation by microorganisms), whereby water treatment can be performed stably for a long period of time.

The reverse osmosis membrane treatment in the present embodiment is at least performed by reverse osmosis membrane treatment, and may include at least an RO membrane treatment apparatus. Further, the reverse osmosis membrane treatment for removing impurities (salts, organic substances, etc.) and the like can be provided in a general water treatment apparatus or water treatment system for performing pure hydration, seawater desalination, etc. The reverse osmosis membrane treatment can be applied to, for example, an ultrapure water treatment manufacturing process, a drain recovery process, a seawater desalination process, and the like.

The water treatment system (or water treatment apparatus) including the RO membrane treatment process of the present embodiment preferably includes a treatment system in which any one or a combination of a plurality of biological treatment process, coagulation treatment process, precipitation treatment process, pressure floating treatment process, solid-liquid separation process, sand filtration treatment process, membrane (MF, UF, etc.) treatment process, and the like is performed. In addition, these processing steps may be performed using a processing apparatus.

In addition, the reverse osmosis membrane treatment or the water treatment system having the reverse osmosis membrane treatment according to the present embodiment is preferably disposed in a different order or sequentially and includes an aggregation treatment step, a solid-liquid separation treatment step, and a turbidity removal membrane treatment step. In addition, these processing steps may be performed using a processing apparatus.

Thus, the RO water supply in which any one of these treatment steps (or apparatuses) or any combination of these treatment steps (or apparatuses) is subjected to pretreatment can be obtained. The turbidity removal membrane treatment is not particularly limited, and examples thereof include a microfiltration membrane (MF membrane) treatment and an ultrafiltration membrane (UF) treatment, and 1 or 2 or more of these may be used in combination. In this way, the impurity in the RO water supply can be reduced, and the RO membrane treatment system can be stably operated for a longer period of time, so that it is preferable to perform pretreatment before performing RO membrane treatment.

The water passing conditions in the present embodiment may be appropriately set according to the RO membrane separation treatment, and examples thereof include a target recovery rate, a water supply pressure (MPa) of the water to be treated, a water supply pH of the water to be treated, and a water supply amount (mL/min) of the water to be treated.

In order to efficiently run the RO membrane separation process for a long period of time, the target water recovery rate may be set to about 60%, preferably about 30 to 50%, and the supply water pressure may be set to about 4 to 8 MPa.

The pH of the water to be treated in the present embodiment is not particularly limited, but is preferably 3.0 to 9.0, more preferably 4.0 to 8.0, and even more preferably 5.0 to 7.0. The pH can be adjusted by the pH adjuster, and according to this pH range, the chemical used in the present embodiment can be effectively used, and the RO membrane separation process can be stably and satisfactorily operated for a long period of time.

The method of the present embodiment can also be implemented by a control unit including a CPU or the like in an apparatus (for example, a computer, a PLC or the like) for managing water quality. The method of the present embodiment may be stored as a program in a hardware resource including a storage medium (a nonvolatile memory (such as a USB memory), an HDD, a CD, or the like) and the like, and may be implemented by the control unit. The control unit can also provide a membrane separation treatment system or a water treatment system or these devices for controlling the addition of a chemical to the water to be treated. The management device may also include an input unit such as a keyboard, a communication unit such as a network, a display unit such as a display, and the like.

< 2-1. Example 1 of the embodiment of the invention >

Next, example 1 of the embodiment of the present invention will be described with reference to fig. 1, but the present invention is not limited thereto.

Examples of the water to be treated in example 1 of the present embodiment include seawater, river water, well water, lake water, industrial water, city water supply, drainage, and drainage treatment water. The water to be treated may contain organic substances, and by applying the present invention to industrial wastewater treatment or the like, treated water (for example, reclaimed water, pure water, ultrapure water, or the like) from which organic compounds have been removed can be obtained. The treated water may contain salt, and by applying the present invention to seawater desalination or the like, treated water (e.g., beverage water, pure water, ultrapure water, etc.) from which salt has been removed can be obtained.

Fig. 1 shows a water treatment system 30 according to the present embodiment, and shows a flowchart of a water treatment system 30 having an RO membrane treatment system 31 including an RO membrane, which is representative of the present embodiment. The water treatment process comprises the following steps: an aggregation treatment step 32 of adding an aggregation agent to water to be treated (raw water), a solid-liquid separation step 33 of treating the aggregation treated water by a solid-liquid separation device, a prefilter treatment step 34, and a reverse osmosis membrane treatment step 31 of treating the water by an RO membrane treatment device. The membrane separation treatment of the reverse osmosis membrane is performed by performing short-term intermittent addition of the chlorine-binding agent as described above as the method of the present invention, before the RO membrane treatment 31 in the prefilter treatment step 34.

The chlorine-binding agent in this embodiment is added to the water to be treated before passing through the RO membrane. The addition is preferably performed between before the RO membrane treatment and after the flocculation treatment, and more preferably between the RO membrane treatment and the prefilter treatment.

By adding the chlorine-binding agent to the water to be treated before passing through the RO membrane, the amount of biofilm adhering to the RO membrane surface and the RO membrane separation apparatus (module) can be reduced. Further, the water to be treated can be separated into concentrated water containing organic compounds, salts, and the like contained in the concentrated water and permeate water through the RO membrane treatment step, and permeate water can be obtained as treated water.

Examples

The following test examples, comparative examples, and the like are given to explain embodiments of the present invention. The scope of the present invention is not limited to the examples and the like.

Test examples 1 and 2 >

(methods of test example 1 and test example 2)

For test example 1 (0.5 h exposure→no addition period), a control, 0.5h exposure→0h no addition period (total 0.5 h), 0.5h exposure→0.5h no addition period (total 1.0 h), 0.5h exposure→1.5h no addition period (total 2.0 h), 0.5h exposure→2.5h no addition period (total 3.0 h), 0.5h exposure→3.5h no addition period (total 4.0 h), 0.5h exposure→4.5h no addition period (total 5.0 h), 0.5h exposure→5.5h no addition period (total 6.0 h), 0.5h exposure→6.5h no addition period (total 7.0 h) each 6 well plate (total 9 groups).

For test example 2 (1 h exposure to no addition period), a control, 1h exposure to 0h no addition period (total 1.0 h), 1h exposure to 1h no addition period (total 2.0 h), 1h exposure to 2h no addition period (total 3.0 h), 1h exposure to 3h no addition period (total 4.0 h), 1h exposure to 4h no addition period (total 5.0 h), 1h exposure to 5h no addition period (total 6.0 h), 1h exposure to 6h no addition period (total 7.0 h) were prepared for each 6 well plate (total 8 groups).

Next, 5mL of seawater medium (Difco) was added to each well of each plate ^TM Marine fungus broth 2216) (37.4 g/L) (see Table 1). To each well was added a suspension containing 1mL of microorganism to reach the viable cell count: 3X 10 ⁵ count/mL (log count/mL is 5 or more). A2 cm. Times.2 cm SWC 5-4040 film (Nito electric Co., ltd. (Nitto Denko Corpora)Condition society manufacturing: polyamide series) are placed in each well and immersed in a seawater medium. The 6-well plate after bacterial attachment was incubated with an orbital shaker at 180rpm at 37 ℃.

[ suspension of microorganism ]

The seawater medium containing the suspension of microorganisms was incubated with an orbital shaker at 180rpm at 37 ℃. The solution containing the overnight culture of bacteria was centrifuged at 4500rpm for 20 minutes and the 2 tubes were pooled. The bacterial suspension was diluted with about 65mL of 0.85% nacl. Dilutions containing the bacteria were used for test example 1 and test example 2.

The bacteria used in this test example can be bacillus species that pass seawater through the reverse osmosis membrane for a predetermined period of time and adhere to the reverse osmosis membrane. In this test example, the BF1 strain obtained by the following procedure was used. Specifically, BF1 strain used in the batch test was extracted from a biofouling membrane (sequoyins) obtained by operating a laboratory scale Reverse Osmosis (RO) system using raw seawater in the western part of singapore. The BF1 strain was identified as Bacillus acidophilus (Bacillus acidicola) based on the result of 16SrRNA sequencing.

TABLE 1

After one day of incubation, the seawater medium in the wells was discarded and replaced with seawater medium containing the binding chlorinating agent. The seawater culture medium containing the binding chlorine agent is prepared by mixing the binding chlorine agent and the seawater culture medium so that the concentration of the binding chlorine reaches 3mg/L based on the binding chlorine. Thus, the SWC5-4040 membrane was immersed in a seawater medium containing a binding chlorine agent to expose it.

Each 6-well plate of test example 1 and test example 2 was subjected to exposure for 0.5 hours and exposure for 1 hour, respectively. The exposure period was taken as an intermittent addition water supply period.

[ Chlorination agent ]

For the combined chlorine agent, a solution was prepared from sodium hypochlorite containing 2% (as available chlorine (Cl) ₂ ) Concentration of sulfamic acid (R) ¹ And R is ² Narrow sulfamic acid of =h) 8% and sodium hydroxide 1% at pH13, was used for test example 1 and test example 2.

In addition, when the combined chlorine agent is used, the free chlorine is not more than the detection limit, and therefore, the combined chlorine concentration in the water to be treated is the total chlorine concentration in the water to be treated.

After a predetermined period of exposure to each well, the seawater medium containing the chlorine binding agent in each well was discarded, and replaced with the addition of 6mL of 1 XPBS (phosphate buffered saline). The state after adding the PBS was set to a state in which no chlorine-binding agent was added, and the no-addition period was defined as a no-addition water supply period. Each 6-well plate was allowed to pass through a predetermined period, and the characteristics of each film were confirmed from the intermittent water supply period to the non-addition water supply period.

In addition, as each control of test example 1 and test example 2, the culture medium was not replaced with the culture medium containing the above-mentioned chlorine-binding agent, and the culture medium was directly incubated with seawater, and PBS was not replaced, and further incubated. For the control of test example 1, the total incubation was 7.5 hours, and for the control of test example 2, the total incubation was 8 hours.

Characterization of films and suspensions

The 2X 2cm membranes in each well plate were removed, each membrane was immersed in 10mL of sterilized 0.85% NaCl solution, and each solution was stirred for 3 minutes. The membrane was then stirred for 10 seconds to separate the biofilm from the membrane surface for protein and cell viability analysis. This operation was performed on each well plate of test example 1 and test example 2, and these were used as each sample solution.

As a feature of the membrane, the number of viable bacteria, the total ATP amount, and the total protein amount of the bacteria were measured using each sample solution.

(method for measuring Total protein)

Quantification of protein content in extracellular polysaccharide was performed using a bicinchoninic acid (BCA) micro protein assay kit (Pierce, # 23235). 1mL of the working solution (reaction reagent) was added to 1mL of the sample solution to obtain a mixed solution. The mixture was incubated in the dark at room temperature for 20 minutes. Next, UV absorbance was measured at 562nm (A562). This operation was performed for each sample solution. Standard calibration curves were plotted using assays with bovine serum albumin (BSA, pierce).

(method for counting viable count)

Viable bacteria count (cell viability) was quantified using a flow cytometer (BD Biosciences, usa). With 1. Mu.L of SYTO, respectively ^(R) Pigment 9 and PI (Propidium iodide) pigment (LIVE/DEAD) ^(R) BacLight ^TM Bacterial viability kit: molecular probes, usa) 1mL of the sample solution was stained. In addition, SYTO for the maximum excitation/luminescence wavelength of these pigments ^(R) The 9 pigment is 480/500nm and the PI pigment is 490/635nm. The sample solution was transferred to a flat bottom well plate for flow cytometry analysis (unstained sample was used as a control). Results were processed using proprietary software (CSampler, BD, usa). Counts within defined areas of density plotted points were converted to living and dead cells. This operation was performed for each sample solution.

(method for measuring Total ATP)

The biofilm was extracted from a 2×2cm piece of membrane using a cotton swab, immersed in 10mL of ultrapure water (MilliQ water, product name) for 2 minutes. ATP of the extracted biofilm was measured using an ATP measuring kit of Japanese tortoise plastron (doctor) コ and a fluorescence detector (fluorescence detector C-110: japanese tortoise plastron (doctor) コ doctor).

< test results >

The measurement results of "total protein amount", "viable cell count (count)", and "total ATP amount" of the drug of test example 1 when exposed to the drug for 0.5 hours are shown in tables 2, 3, and 4, respectively, and these results are shown in fig. 2. The measurement results of the "total protein amount" of the drug of test example 2 when exposed for 1 hour are shown in table 5.

TABLE 2

* 1) Post-dosing time (h) =exposure time (h) +no-addition period (h)

* 2) (h): control

TABLE 3 Table 3

* 1) Post-dosing time (h) =exposure time (h) +no-addition period (h)

* 2) (h): control

TABLE 4 Table 4

* 1) Post-dosing time (h) =exposure time (h) +no-addition period (h)

* 2) (h): control

TABLE 5

* 1) Post-dosing time (h) =exposure time (h) +no-addition period (h)

* 2) (h): control

In reverse osmosis membranes in which microorganisms were present in the biofilm, as shown in tables 2 to 4 and fig. 2, when the membrane was exposed to a chlorine-binding agent containing a sulfamic acid compound for 0.5 hour and then subjected to a condition of no addition of a chemical agent for 0.5 to 6.0 hours, the total protein amount and the viable count of microorganisms were significantly reduced in comparison with the initial 0 hour (control), and the activity of microorganisms could be suppressed very efficiently. In addition, in general, the total ATP amount tends to increase rapidly before the proliferation rate increases and the subsequent production amount of metabolites increases.

As shown in table 5, when the chlorine-binding agent containing the sulfamic acid compound was exposed for 1.0 hour and then 1.0 to 6.0 hours passed without adding the chemical agent, the total protein mass was significantly reduced in comparison with the initial 0 hour (control), and the activity of the microorganism was extremely effectively inhibited.

Therefore, in the present test examples 1 and 2, the exposure time was 0.5 to 1 hour, and then the rapid rise was observed from 6.5 hours or around 6 hours in the state where no chemical was added, and therefore, if the state where no chemical was added reached 6 hours, it was considered that the activity of microorganisms could be effectively inhibited. As described above, in the present test examples 1 and 2, the microbial activity was inhibited by exposure for 0.5 to 1 hour and then by passage of 0.5 to 6.0 hours without adding the chemical, and it was confirmed that the formation of the biofilm was also inhibited.

Conventionally, since the separation of a biofilm formed with microorganisms has been focused, it is considered that water treatment can be continued more stably for a long period of time without addition in reverse osmosis membrane separation. In contrast, the present inventors have found that, as a result of a test performed after temporarily proliferating and activating a microorganism (i.e., a result focusing on the activity of the microorganism), it is novel that: in reverse osmosis membrane separation, when water treatment is stably continued for a long period of time, there is a short-term intermittent addition method.

In view of the effects, cost, and the like of test examples 1 and 2 of the present application, it is considered that the exposure period is preferably 0.25 to 5 hours. Thus, the time for one cycle is preferably 1.25 to 11 hours, more preferably 1.5 to 7 hours.

As described above, the activity of microorganisms in the biofilm can be inhibited by intermittent addition of the chlorine-binding agent for a short period of time. Thus, in reverse osmosis membrane separation, water treatment can be stably continued for a long period of time by using the short-term intermittent addition conditions of the present invention.

The average concentration of the chlorine-binding agent in the water to be treated was calculated as 3mg/L of the chlorine-binding agent in the medium by the exposure period (h)/one cycle period (h).

The exposure was performed at a combined chlorine concentration in the medium of 3mg/L in terms of combined chlorine, so that, when the exposure period of 0.5h and the no-addition period of 1 to 6h were taken as one cycle, the average concentration of the combined chlorine agent in the treated water was 1.00, 0.60, 0.42, 0.33, 0.27, 0.23mg/L in terms of combined chlorine, when the no-addition period was 1h, 2h, 3h, 4h, 5h, 6h, respectively, in each cycle.

Since the exposure was performed at a combined chlorine concentration in the medium of 3mg/L, when 1h and 1 to 6h of the non-addition period were used as one cycle, the average concentration of the combined chlorine agent in the water to be treated was 1.50, 1.00, 0.75, 0.60, 0.50, and 0.43mg/L in combined chlorine when 1h, 2h, 3h, 4h, 5h, and 6h of the non-addition period were used in each cycle.

Thus, it is considered that the average concentration of the chlorine-binding agent in the water to be treated in each cycle is preferably 0.05 to 1.5mg/L in terms of chlorine-binding agent, more preferably 0.1 to 1.0mg/L in terms of chlorine-binding agent, still more preferably 0.2 to 1.0mg/L in terms of chlorine-binding agent.

In addition, since the composition ratio of the chlorine-based oxidizing agent to the alkali metal component in the medium during the exposure period was 2X 10 in terms of the molar ratio of Cl/alkali metal ^-5 ～1×10 ^-3 Therefore, this range is preferable.

In addition, since the ratio of Br to Cl in the medium during the exposure period was 5X 10 in terms of Br/Cl molar ratio ^-3 Hereinafter, this range is considered preferable.

In addition, since the number of viable bacteria in the medium before the start of the test was 3X 10 ⁵ The effect of the present invention can be exhibited satisfactorily when the number of viable bacteria (log count/mL) reaches 5, and further, the number of viable bacteria (log count/mL) in the water to be treated is 4 or less and 3 or less, or further, it is considered that the effect of the present invention can be exhibited more satisfactorily by carrying out the present invention on microorganisms smaller than 3.

Reference test example 3 and test example 4 >

Reference test examples 3 and 4 were conducted under the following experimental conditions in the test factories. The same chlorine-binding agent as that used in the above-described test examples 1 and 2 was used as the chlorine-binding agent used in reference test example 3 and test example 4. In addition, since the free chlorine concentration of the combined chlorine agent is equal to or lower than the detection limit, the combined chlorine concentration in the water to be treated=the total chlorine concentration in the water to be treated.

The device configuration is shown in fig. 3.

The treated water obtained by treating the impurity-removed seawater with the ultrafiltration membrane is stored in the raw water storage tank 51 as raw water. The raw water flows from the raw water storage tank 51 into the supply tank 52. SBS is added to the flow path between the raw water storage tank 51 and the supply tank 52 for the purpose of preventing biofouling to achieve T-Cl ₂ (perchloric concentration) < 0.1mg/L and ORP < 300mV. The raw water after SBS treatment was transferred from the supply tank 52 to the prefilter (3 μm) 53 by a pump. A scale inhibitor (SD) was added to the flow path between the supply tank 52 and the prefilter 53, and a Combined Chlorine Agent (CCA) was added simultaneously or separately under the following < combined chlorine addition conditions >. The treated raw water was subjected to membrane treatment by a prefilter (3 μm) 53. The raw water after the prefilter treatment was transferred to a reverse osmosis membrane apparatus (SWRO, 4 inch, 4 element, nitto SWC 5) 54 by a pump. The transferred raw water was treated by the reverse osmosis membrane device 54 to reach flux=0.35 m/d. After the RO membrane treatment, the raw water is separated into permeate (fresh water) and drain (concentrate).

As raw water (ultrafiltrate), raw water obtained by treating seawater from which impurities have been removed with an ultrafiltration membrane is used. Sodium hypochlorite is added to treat the raw water without adding an coagulant in order to prevent biofouling of the ultrafiltration membrane apparatus or the like.

As SD: as the Scale Dispersant (SD), kuriveter N300 (manufactured by Japanese chestnut field Co., ltd.) was used.

CCA was used: a chlorine-binding agent (Conbined chlorine agent: CCA) containing a sulfamic acid compound is added to the water to be treated during intermittent addition of the water supply to achieve a concentration of "in chlorine-binding".

In addition, in the detection after the addition of the water to be treated, the free chlorine is not more than the detection limit for the used chlorine-binding agent, and therefore, the concentration of the chlorine-binding agent in the water to be treated is the total chlorine concentration in the water to be treated.

SBS: sodium Bisulphite (SBS) is used to reduce the sodium hypochlorite added for the sterilization of raw seawater.

The film used: SWC5-4040 by eastern electrician, aromatic polyamide RO membrane.

Film flow rate: 0.063 m/s.

Recovery rate: 45%.

Raw water: sea water.

Temperature: 30-35 ℃.

pH：7～8。

Conditions for < combined chlorine addition: intermittent water supply and no water supply condition >)

The water treatment operation was performed in the following order of the first to fifth steps.

As shown in FIG. 4, the first half (second step and third step) was operated under intermittent addition conditions during intermittent addition of water (1 h; 1.2 to 2.4mg/L in combination with chlorine addition to combination with chlorine meter) and during no addition of water (7 h), and this was taken as reference test example 3. In the latter half (fourth step and fifth step), the test example 4 was conducted under the short-term intermittent addition conditions of the present invention, specifically, during intermittent addition of water supply (0.5 h; 2.4 to 1.8mg/L in combination with chlorine addition amount) and during no addition of water supply (3.5 h).

A first step of: the chlorine-binding agent is continuously added for 2 weeks under the condition that the concentration of the chlorine-binding agent in the water to be treated is 0.48-0.6 mg/L.

And a second step of: then, the water treatment was performed between days 5 and 7 and 23 under the conditions of repeating one cycle of adding water for 1 hour (the addition amount of the chlorine-binding agent: the concentration of the chlorine-binding agent in the water to be treated, 1.2 mg/L) and adding no water for 7 hours.

And a third step of: the water treatment was performed between 24 days and 27 days in 5 months under the condition of repeating one cycle of adding water supply for 1 hour (addition amount of the chlorine-binding agent: concentration of chlorine-binding agent in the water to be treated, 2.4 mg/L) and adding no water supply for 7 hours.

Fourth step: further, the operation of water treatment was carried out between days 5 and 27 and 6 and 18 under the condition that one cycle of adding water supply period of 0.5 hours (addition amount of the chlorine-binding agent: concentration of chlorine-binding agent in the water to be treated, 2.4 mg/L) and no water supply period of 3.5 hours was repeated.

Fifth step: further, the operation of water treatment was performed between 19 days and 30 days of 6 months under the condition that one cycle of adding water supply period of 0.5 hours (addition amount of the binding chlorine agent: concentration of binding chlorine in the water to be treated, 1.8 mg/L) and no water supply period of 3.5 hours was repeated, which corresponds to the present invention.

< test results >

Fig. 4 shows the change in RO membrane pressure in the water system. Reference test example 3 (second to third steps) in the first half corresponds to the intermittent addition condition of patent document 3. The second half is a test example 4 (fourth to fifth steps) corresponding to the present invention.

The second step starts for 5 months and 7 days: film pressure, delta pressure 0.107Mpa; the third step ends for 5 months and 27 days: membrane pressure, delta pressure 0.165Mpa, running days 20 days.

The slope from the beginning of the second step to the end of the third step was 0.0029MPa/1 day.

The fourth step starts for 5 months and 28 days: film pressure, delta pressure 0.165Mpa; the fifth step is finished for 6 months and 30 days: film pressure, delta pressure 0.210Mpa; the number of days of operation was 33 days.

The slope from the beginning of the fourth step to the end of the fifth step was 0.0014MPa/1 day.

In the reverse osmosis membrane system of the test plant, the membrane pressure was well suppressed in the reference test example 3, but when the slope of the change in the membrane pressure of the reference test example 3 was compared with the slope of the test example 4 corresponding to the present invention, the slope of the test example 4 was about half or less than that of the reference test example 3. Since the water treatment can be stably continued for a long period of time in the reverse osmosis membrane treatment as the slope of the membrane pressure change is smaller, the present invention has proved to have a very remarkable excellent effect from the viewpoint of stably and continuously conducting the water treatment for a long period of time as compared with the method of the intermittent addition condition of patent document 3. Further, as shown in test examples 1 and 2, the short-term intermittent addition conditions of the present invention are conditions that can favorably inhibit the activity of microorganisms in a biofilm.

In this case, the present invention can inhibit the activity of microorganisms in the biofilm, has a particularly remarkable effect as compared with the conventional method, and can stably and continuously perform the water treatment by reverse osmosis membrane separation for a long period of time.

Industrial applicability

The present invention can be used for a method of performing membrane separation by supplying water to be treated to a membrane separation apparatus having a permeable membrane such as a reverse osmosis membrane. In particular, the present invention can be applied to a membrane separation method in which the activity of microorganisms in a biofilm can be suppressed and water treatment can be stably continued for a long period of time by adding a chlorine-binding agent containing a sulfamic acid compound to the water supply of a membrane separation apparatus under intermittent addition conditions for a short period of time.

Description of the reference numerals

30: a water treatment system; 31: RO membrane treatment apparatus (RO membrane treatment step); 32: an aggregation device (aggregation treatment step); 33: a solid-liquid separation device (solid-liquid separation treatment step); 34: MF membrane apparatus (prefilter treatment step); 50: a water treatment system; 51: a raw water storage tank; 52: a supply tank; 53: a prefilter; 54: RO membrane treatment device; p: a pump; SBS: sodium bisulfite; SD: a soil dispersing agent; CCA: and (3) combining a chlorinating agent.

Claims

1. A membrane separation method comprising adding a chlorine-binding agent containing an sulfamic acid compound to water to be treated supplied to a reverse osmosis membrane separation apparatus to perform membrane separation treatment,

The intermittent addition is repeated between an intermittent addition water supply period in which the concentration of the chlorine-binding agent for inhibiting the activity of microorganisms in the biofilm is set to 0.3 to 10mg/L and water is supplied to the reverse osmosis membrane separation device and a non-addition water supply period in which water is supplied to the reverse osmosis membrane separation device without adding the chlorine-binding agent,

the intermittent addition of water is for 0.25 to 5 hours,

the non-additive water supply period is 1 hour or more and 5.5 hours or less.

2. The membrane separation method according to claim 1, wherein when one intermittent water supply period and one non-additive water supply period are taken as one cycle, the time of the one cycle is 1.25 to 10 hours.

3. The membrane separation method according to claim 1 or 2, wherein the time ratio of the no-addition water supply period/the intermittent-addition water supply period is 0.2 to 20.

4. The membrane separation method according to claim 1 or 2, wherein the intermittent addition water supply period is 0.5 to 1 hour and/or the no addition water supply period is 1 to 4 hours.

5. The membrane separation method according to claim 1 or 2, wherein when one intermittent water supply period and one non-addition water supply period are taken as one cycle, an average concentration of the chlorine-binding agent in the water to be treated in each cycle is 0.05 to 1.5mg/L in terms of the chlorine-binding agent.

6. The membrane separation method according to claim 1 or 2, wherein the membrane separation method is operated in a range of 0 to 50000mg/L of salt concentration in the water to be treated.

7. The membrane separation method according to claim 1 or 2, wherein the composition ratio of the chlorine-based oxidizing agent to the alkali metal component in the water to be treated in the intermittent addition of the water supply period is 2X 10 in terms of a molar ratio of Cl/alkali metal ^-5 ～1×10 ^-3 。

8. The membrane separation method according to claim 1 or 2, wherein the ratio of Br to Cl in the water to be treated during the intermittent addition of water supply is 5X 10 in terms of molar ratio of Br/Cl ^-3 The following is given.

9. The membrane separation method according to claim 1 or 2, wherein the membrane surface of the separation membrane is operated at a flow rate of 4 cm/sec to 15 cm/sec.

10. A membrane separation process according to claim 3, wherein the intermittent feed water supply period is 0.5 to 1 hour and/or the no feed water period is 1 to 4 hours.

11. The membrane separation method according to claim 3, wherein when one intermittent water supply period and one non-additive water supply period are used as one cycle, an average concentration of the chlorine-binding agent in the water to be treated is 0.05 to 1.5mg/L in terms of the chlorine-binding agent per one cycle.

12. The membrane separation method according to claim 10, wherein when one intermittent water supply period and one non-addition water supply period are taken as one cycle, an average concentration of the chlorine-binding agent in the water to be treated in each cycle is 0.05 to 1.5mg/L in terms of the chlorine-binding agent.